Air cylinder apparatuses are used as a power source for various devices. Among them, in an air cylinder apparatus such as a depositor, a bonder or a precision polishing machine that is used in a manner to move a workpiece up and down by a piston rod that is slidably fitted into a cylinder body, an apparatus which locks the piston rod to the cylinder body at an ascending position (specific position) of the piston rod so that the workpiece does not fall upon an occurrence of an air leakage, an air shortage, or the like, in the air cylinder apparatus has been proposed. See Japanese Unexamined Utility Model Publication No. H05-75503.